includes/libs/rdbms/database/DatabaseMssql.php

   1 <?php
   2 /**
   3  * This is the MS SQL Server Native database abstraction layer.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Database
  22  * @author Joel Penner <a-joelpe at microsoft dot com>
  23  * @author Chris Pucci <a-cpucci at microsoft dot com>
  24  * @author Ryan Biesemeyer <v-ryanbi at microsoft dot com>
  25  * @author Ryan Schmidt <skizzerz at gmail dot com>
  26  */
  27
  28 namespace Wikimedia\Rdbms;
  29
  30 use Wikimedia;
  31 use Exception;
  32 use stdClass;
  33
  34 /**
  35  * @ingroup Database
  36  */
  37 class DatabaseMssql extends Database {
  38         /** @var int */
  39         protected $serverPort;
  40         /** @var bool */
  41         protected $useWindowsAuth = false;
  42         /** @var int|null */
  43         protected $lastInsertId = null;
  44         /** @var int|null */
  45         protected $lastAffectedRowCount = null;
  46         /** @var int */
  47         protected $subqueryId = 0;
  48         /** @var bool */
  49         protected $scrollableCursor = true;
  50         /** @var bool */
  51         protected $prepareStatements = true;
  52         /** @var stdClass[][]|null */
  53         protected $binaryColumnCache = null;
  54         /** @var stdClass[][]|null */
  55         protected $bitColumnCache = null;
  56         /** @var bool */
  57         protected $ignoreDupKeyErrors = false;
  58         /** @var string[] */
  59         protected $ignoreErrors = [];
  60
  61         public function implicitGroupby() {
  62                 return false;
  63         }
  64
  65         public function implicitOrderby() {
  66                 return false;
  67         }
  68
  69         public function unionSupportsOrderAndLimit() {
  70                 return false;
  71         }
  72
  73         public function __construct( array $params ) {
  74                 $this->serverPort = $params['port'];
  75                 $this->useWindowsAuth = $params['UseWindowsAuth'];
  76
  77                 parent::__construct( $params );
  78         }
  79
  80         protected function open( $server, $user, $password, $dbName, $schema, $tablePrefix ) {
  81                 # Test for driver support, to avoid suppressed fatal error
  82                 if ( !function_exists( 'sqlsrv_connect' ) ) {
  83                         throw new DBConnectionError(
  84                                 $this,
  85                                 "Microsoft SQL Server Native (sqlsrv) functions missing.
  86                                 You can download the driver from: http://go.microsoft.com/fwlink/?LinkId=123470\n"
  87                         );
  88                 }
  89
  90                 # e.g. the class is being loaded
  91                 if ( !strlen( $user ) ) {
  92                         return null;
  93                 }
  94
  95                 $this->close();
  96                 $this->server = $server;
  97                 $this->user = $user;
  98                 $this->password = $password;
  99
 100                 $connectionInfo = [];
 101
 102                 if ( $dbName != '' ) {
 103                         $connectionInfo['Database'] = $dbName;
 104                 }
 105
 106                 // Decide which auth scenerio to use
 107                 // if we are using Windows auth, then don't add credentials to $connectionInfo
 108                 if ( !$this->useWindowsAuth ) {
 109                         $connectionInfo['UID'] = $user;
 110                         $connectionInfo['PWD'] = $password;
 111                 }
 112
 113                 Wikimedia\suppressWarnings();
 114                 $this->conn = sqlsrv_connect( $server, $connectionInfo );
 115                 Wikimedia\restoreWarnings();
 116
 117                 if ( $this->conn === false ) {
 118                         throw new DBConnectionError( $this, $this->lastError() );
 119                 }
 120
 121                 $this->opened = true;
 122                 $this->currentDomain = new DatabaseDomain(
 123                         ( $dbName != '' ) ? $dbName : null,
 124                         null,
 125                         $tablePrefix
 126                 );
 127
 128                 return (bool)$this->conn;
 129         }
 130
 131         /**
 132          * Closes a database connection, if it is open
 133          * Returns success, true if already closed
 134          * @return bool
 135          */
 136         protected function closeConnection() {
 137                 return sqlsrv_close( $this->conn );
 138         }
 139
 140         /**
 141          * @param bool|MssqlResultWrapper|resource $result
 142          * @return bool|MssqlResultWrapper
 143          */
 144         protected function resultObject( $result ) {
 145                 if ( !$result ) {
 146                         return false;
 147                 } elseif ( $result instanceof MssqlResultWrapper ) {
 148                         return $result;
 149                 } elseif ( $result === true ) {
 150                         // Successful write query
 151                         return $result;
 152                 } else {
 153                         return new MssqlResultWrapper( $this, $result );
 154                 }
 155         }
 156
 157         /**
 158          * @param string $sql
 159          * @return bool|MssqlResultWrapper|resource
 160          */
 161         protected function doQuery( $sql ) {
 162                 // several extensions seem to think that all databases support limits
 163                 // via LIMIT N after the WHERE clause, but  MSSQL uses SELECT TOP N,
 164                 // so to catch any of those extensions we'll do a quick check for a
 165                 // LIMIT clause and pass $sql through $this->LimitToTopN() which parses
 166                 // the LIMIT clause and passes the result to $this->limitResult();
 167                 if ( preg_match( '/\bLIMIT\s*/i', $sql ) ) {
 168                         // massage LIMIT -> TopN
 169                         $sql = $this->LimitToTopN( $sql );
 170                 }
 171
 172                 // MSSQL doesn't have EXTRACT(epoch FROM XXX)
 173                 if ( preg_match( '#\bEXTRACT\s*?\(\s*?EPOCH\s+FROM\b#i', $sql, $matches ) ) {
 174                         // This is same as UNIX_TIMESTAMP, we need to calc # of seconds from 1970
 175                         $sql = str_replace( $matches[0], "DATEDIFF(s,CONVERT(datetime,'1/1/1970'),", $sql );
 176                 }
 177
 178                 // perform query
 179
 180                 // SQLSRV_CURSOR_STATIC is slower than SQLSRV_CURSOR_CLIENT_BUFFERED (one of the two is
 181                 // needed if we want to be able to seek around the result set), however CLIENT_BUFFERED
 182                 // has a bug in the sqlsrv driver where wchar_t types (such as nvarchar) that are empty
 183                 // strings make php throw a fatal error "Severe error translating Unicode"
 184                 if ( $this->scrollableCursor ) {
 185                         $scrollArr = [ 'Scrollable' => SQLSRV_CURSOR_STATIC ];
 186                 } else {
 187                         $scrollArr = [];
 188                 }
 189
 190                 if ( $this->prepareStatements ) {
 191                         // we do prepare + execute so we can get its field metadata for later usage if desired
 192                         $stmt = sqlsrv_prepare( $this->conn, $sql, [], $scrollArr );
 193                         $success = sqlsrv_execute( $stmt );
 194                 } else {
 195                         $stmt = sqlsrv_query( $this->conn, $sql, [], $scrollArr );
 196                         $success = (bool)$stmt;
 197                 }
 198
 199                 // Make a copy to ensure what we add below does not get reflected in future queries
 200                 $ignoreErrors = $this->ignoreErrors;
 201
 202                 if ( $this->ignoreDupKeyErrors ) {
 203                         // ignore duplicate key errors
 204                         // this emulates INSERT IGNORE in MySQL
 205                         $ignoreErrors[] = '2601'; // duplicate key error caused by unique index
 206                         $ignoreErrors[] = '2627'; // duplicate key error caused by primary key
 207                         $ignoreErrors[] = '3621'; // generic "the statement has been terminated" error
 208                 }
 209
 210                 if ( $success === false ) {
 211                         $errors = sqlsrv_errors();
 212                         $success = true;
 213
 214                         foreach ( $errors as $err ) {
 215                                 if ( !in_array( $err['code'], $ignoreErrors ) ) {
 216                                         $success = false;
 217                                         break;
 218                                 }
 219                         }
 220
 221                         if ( $success === false ) {
 222                                 return false;
 223                         }
 224                 }
 225                 // remember number of rows affected
 226                 $this->lastAffectedRowCount = sqlsrv_rows_affected( $stmt );
 227
 228                 return $stmt;
 229         }
 230
 231         public function freeResult( $res ) {
 232                 if ( $res instanceof ResultWrapper ) {
 233                         $res = $res->result;
 234                 }
 235
 236                 sqlsrv_free_stmt( $res );
 237         }
 238
 239         /**
 240          * @param IResultWrapper $res
 241          * @return stdClass
 242          */
 243         public function fetchObject( $res ) {
 244                 // $res is expected to be an instance of MssqlResultWrapper here
 245                 return $res->fetchObject();
 246         }
 247
 248         /**
 249          * @param IResultWrapper $res
 250          * @return array
 251          */
 252         public function fetchRow( $res ) {
 253                 return $res->fetchRow();
 254         }
 255
 256         /**
 257          * @param mixed $res
 258          * @return int
 259          */
 260         public function numRows( $res ) {
 261                 if ( $res instanceof ResultWrapper ) {
 262                         $res = $res->result;
 263                 }
 264
 265                 $ret = sqlsrv_num_rows( $res );
 266
 267                 if ( $ret === false ) {
 268                         // we cannot get an amount of rows from this cursor type
 269                         // has_rows returns bool true/false if the result has rows
 270                         $ret = (int)sqlsrv_has_rows( $res );
 271                 }
 272
 273                 return $ret;
 274         }
 275
 276         /**
 277          * @param mixed $res
 278          * @return int
 279          */
 280         public function numFields( $res ) {
 281                 if ( $res instanceof ResultWrapper ) {
 282                         $res = $res->result;
 283                 }
 284
 285                 return sqlsrv_num_fields( $res );
 286         }
 287
 288         /**
 289          * @param mixed $res
 290          * @param int $n
 291          * @return int
 292          */
 293         public function fieldName( $res, $n ) {
 294                 if ( $res instanceof ResultWrapper ) {
 295                         $res = $res->result;
 296                 }
 297
 298                 return sqlsrv_field_metadata( $res )[$n]['Name'];
 299         }
 300
 301         /**
 302          * This must be called after nextSequenceVal
 303          * @return int|null
 304          */
 305         public function insertId() {
 306                 return $this->lastInsertId;
 307         }
 308
 309         /**
 310          * @param MssqlResultWrapper $res
 311          * @param int $row
 312          * @return bool
 313          */
 314         public function dataSeek( $res, $row ) {
 315                 return $res->seek( $row );
 316         }
 317
 318         /**
 319          * @return string
 320          */
 321         public function lastError() {
 322                 $strRet = '';
 323                 $retErrors = sqlsrv_errors( SQLSRV_ERR_ALL );
 324                 if ( $retErrors != null ) {
 325                         foreach ( $retErrors as $arrError ) {
 326                                 $strRet .= $this->formatError( $arrError ) . "\n";
 327                         }
 328                 } else {
 329                         $strRet = "No errors found";
 330                 }
 331
 332                 return $strRet;
 333         }
 334
 335         /**
 336          * @param array $err
 337          * @return string
 338          */
 339         private function formatError( $err ) {
 340                 return '[SQLSTATE ' .
 341                         $err['SQLSTATE'] . '][Error Code ' . $err['code'] . ']' . $err['message'];
 342         }
 343
 344         /**
 345          * @return string|int
 346          */
 347         public function lastErrno() {
 348                 $err = sqlsrv_errors( SQLSRV_ERR_ALL );
 349                 if ( $err !== null && isset( $err[0] ) ) {
 350                         return $err[0]['code'];
 351                 } else {
 352                         return 0;
 353                 }
 354         }
 355
 356         protected function wasKnownStatementRollbackError() {
 357                 $errors = sqlsrv_errors( SQLSRV_ERR_ALL );
 358                 if ( !$errors ) {
 359                         return false;
 360                 }
 361                 // The transaction vs statement rollback behavior depends on XACT_ABORT, so make sure
 362                 // that the "statement has been terminated" error (3621) is specifically present.
 363                 // https://docs.microsoft.com/en-us/sql/t-sql/statements/set-xact-abort-transact-sql
 364                 $statementOnly = false;
 365                 $codeWhitelist = [ '2601', '2627', '547' ];
 366                 foreach ( $errors as $error ) {
 367                         if ( $error['code'] == '3621' ) {
 368                                 $statementOnly = true;
 369                         } elseif ( !in_array( $error['code'], $codeWhitelist ) ) {
 370                                 $statementOnly = false;
 371                                 break;
 372                         }
 373                 }
 374
 375                 return $statementOnly;
 376         }
 377
 378         /**
 379          * @return int
 380          */
 381         protected function fetchAffectedRowCount() {
 382                 return $this->lastAffectedRowCount;
 383         }
 384
 385         /**
 386          * SELECT wrapper
 387          *
 388          * @param mixed $table Array or string, table name(s) (prefix auto-added)
 389          * @param mixed $vars Array or string, field name(s) to be retrieved
 390          * @param mixed $conds Array or string, condition(s) for WHERE
 391          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
 392          * @param array $options Associative array of options (e.g.
 393          *   [ 'GROUP BY' => 'page_title' ]), see Database::makeSelectOptions
 394          *   code for list of supported stuff
 395          * @param array $join_conds Associative array of table join conditions
 396          *   (optional) (e.g. [ 'page' => [ 'LEFT JOIN','page_latest=rev_id' ] ]
 397          * @return mixed Database result resource (feed to Database::fetchObject
 398          *   or whatever), or false on failure
 399          * @throws DBQueryError
 400          * @throws DBUnexpectedError
 401          * @throws Exception
 402          */
 403         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
 404                 $options = [], $join_conds = []
 405         ) {
 406                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
 407                 if ( isset( $options['EXPLAIN'] ) ) {
 408                         try {
 409                                 $this->scrollableCursor = false;
 410                                 $this->prepareStatements = false;
 411                                 $this->query( "SET SHOWPLAN_ALL ON" );
 412                                 $ret = $this->query( $sql, $fname );
 413                                 $this->query( "SET SHOWPLAN_ALL OFF" );
 414                         } catch ( DBQueryError $dqe ) {
 415                                 if ( isset( $options['FOR COUNT'] ) ) {
 416                                         // likely don't have privs for SHOWPLAN, so run a select count instead
 417                                         $this->query( "SET SHOWPLAN_ALL OFF" );
 418                                         unset( $options['EXPLAIN'] );
 419                                         $ret = $this->select(
 420                                                 $table,
 421                                                 'COUNT(*) AS EstimateRows',
 422                                                 $conds,
 423                                                 $fname,
 424                                                 $options,
 425                                                 $join_conds
 426                                         );
 427                                 } else {
 428                                         // someone actually wanted the query plan instead of an est row count
 429                                         // let them know of the error
 430                                         $this->scrollableCursor = true;
 431                                         $this->prepareStatements = true;
 432                                         throw $dqe;
 433                                 }
 434                         }
 435                         $this->scrollableCursor = true;
 436                         $this->prepareStatements = true;
 437                         return $ret;
 438                 }
 439                 return $this->query( $sql, $fname );
 440         }
 441
 442         /**
 443          * SELECT wrapper
 444          *
 445          * @param mixed $table Array or string, table name(s) (prefix auto-added)
 446          * @param mixed $vars Array or string, field name(s) to be retrieved
 447          * @param mixed $conds Array or string, condition(s) for WHERE
 448          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
 449          * @param array $options Associative array of options (e.g. [ 'GROUP BY' => 'page_title' ]),
 450          *   see Database::makeSelectOptions code for list of supported stuff
 451          * @param array $join_conds Associative array of table join conditions (optional)
 452          *    (e.g. [ 'page' => [ 'LEFT JOIN','page_latest=rev_id' ] ]
 453          * @return string The SQL text
 454          */
 455         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
 456                 $options = [], $join_conds = []
 457         ) {
 458                 if ( isset( $options['EXPLAIN'] ) ) {
 459                         unset( $options['EXPLAIN'] );
 460                 }
 461
 462                 $sql = parent::selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
 463
 464                 // try to rewrite aggregations of bit columns (currently MAX and MIN)
 465                 if ( strpos( $sql, 'MAX(' ) !== false || strpos( $sql, 'MIN(' ) !== false ) {
 466                         $bitColumns = [];
 467                         if ( is_array( $table ) ) {
 468                                 $tables = $table;
 469                                 while ( $tables ) {
 470                                         $t = array_pop( $tables );
 471                                         if ( is_array( $t ) ) {
 472                                                 $tables = array_merge( $tables, $t );
 473                                         } else {
 474                                                 $bitColumns += $this->getBitColumns( $this->tableName( $t ) );
 475                                         }
 476                                 }
 477                         } else {
 478                                 $bitColumns = $this->getBitColumns( $this->tableName( $table ) );
 479                         }
 480
 481                         foreach ( $bitColumns as $col => $info ) {
 482                                 $replace = [
 483                                         "MAX({$col})" => "MAX(CAST({$col} AS tinyint))",
 484                                         "MIN({$col})" => "MIN(CAST({$col} AS tinyint))",
 485                                 ];
 486                                 $sql = str_replace( array_keys( $replace ), array_values( $replace ), $sql );
 487                         }
 488                 }
 489
 490                 return $sql;
 491         }
 492
 493         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
 494                 $fname = __METHOD__
 495         ) {
 496                 $this->scrollableCursor = false;
 497                 try {
 498                         parent::deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds, $fname );
 499                 } catch ( Exception $e ) {
 500                         $this->scrollableCursor = true;
 501                         throw $e;
 502                 }
 503                 $this->scrollableCursor = true;
 504         }
 505
 506         public function delete( $table, $conds, $fname = __METHOD__ ) {
 507                 $this->scrollableCursor = false;
 508                 try {
 509                         parent::delete( $table, $conds, $fname );
 510                 } catch ( Exception $e ) {
 511                         $this->scrollableCursor = true;
 512                         throw $e;
 513                 }
 514                 $this->scrollableCursor = true;
 515
 516                 return true;
 517         }
 518
 519         /**
 520          * Estimate rows in dataset
 521          * Returns estimated count, based on SHOWPLAN_ALL output
 522          * This is not necessarily an accurate estimate, so use sparingly
 523          * Returns -1 if count cannot be found
 524          * Takes same arguments as Database::select()
 525          * @param string $table
 526          * @param string $var
 527          * @param string $conds
 528          * @param string $fname
 529          * @param array $options
 530          * @param array $join_conds
 531          * @return int
 532          */
 533         public function estimateRowCount( $table, $var = '*', $conds = '',
 534                 $fname = __METHOD__, $options = [], $join_conds = []
 535         ) {
 536                 $conds = $this->normalizeConditions( $conds, $fname );
 537                 $column = $this->extractSingleFieldFromList( $var );
 538                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
 539                         $conds[] = "$column IS NOT NULL";
 540                 }
 541
 542                 // http://msdn2.microsoft.com/en-us/library/aa259203.aspx
 543                 $options['EXPLAIN'] = true;
 544                 $options['FOR COUNT'] = true;
 545                 $res = $this->select( $table, $var, $conds, $fname, $options, $join_conds );
 546
 547                 $rows = -1;
 548                 if ( $res ) {
 549                         $row = $this->fetchRow( $res );
 550
 551                         if ( isset( $row['EstimateRows'] ) ) {
 552                                 $rows = (int)$row['EstimateRows'];
 553                         }
 554                 }
 555
 556                 return $rows;
 557         }
 558
 559         /**
 560          * Returns information about an index
 561          * If errors are explicitly ignored, returns NULL on failure
 562          * @param string $table
 563          * @param string $index
 564          * @param string $fname
 565          * @return array|bool|null
 566          */
 567         public function indexInfo( $table, $index, $fname = __METHOD__ ) {
 568                 # This does not return the same info as MYSQL would, but that's OK
 569                 # because MediaWiki never uses the returned value except to check for
 570                 # the existence of indexes.
 571                 $sql = "sp_helpindex '" . $this->tableName( $table ) . "'";
 572                 $res = $this->query( $sql, $fname );
 573
 574                 if ( !$res ) {
 575                         return null;
 576                 }
 577
 578                 $result = [];
 579                 foreach ( $res as $row ) {
 580                         if ( $row->index_name == $index ) {
 581                                 $row->Non_unique = !stristr( $row->index_description, "unique" );
 582                                 $cols = explode( ", ", $row->index_keys );
 583                                 foreach ( $cols as $col ) {
 584                                         $row->Column_name = trim( $col );
 585                                         $result[] = clone $row;
 586                                 }
 587                         } elseif ( $index == 'PRIMARY' && stristr( $row->index_description, 'PRIMARY' ) ) {
 588                                 $row->Non_unique = 0;
 589                                 $cols = explode( ", ", $row->index_keys );
 590                                 foreach ( $cols as $col ) {
 591                                         $row->Column_name = trim( $col );
 592                                         $result[] = clone $row;
 593                                 }
 594                         }
 595                 }
 596
 597                 return $result ?: false;
 598         }
 599
 600         /**
 601          * INSERT wrapper, inserts an array into a table
 602          *
 603          * $arrToInsert may be a single associative array, or an array of these with numeric keys, for
 604          * multi-row insert.
 605          *
 606          * Usually aborts on failure
 607          * If errors are explicitly ignored, returns success
 608          * @param string $table
 609          * @param array $arrToInsert
 610          * @param string $fname
 611          * @param array $options
 612          * @return bool
 613          * @throws Exception
 614          */
 615         public function insert( $table, $arrToInsert, $fname = __METHOD__, $options = [] ) {
 616                 # No rows to insert, easy just return now
 617                 if ( !count( $arrToInsert ) ) {
 618                         return true;
 619                 }
 620
 621                 if ( !is_array( $options ) ) {
 622                         $options = [ $options ];
 623                 }
 624
 625                 $table = $this->tableName( $table );
 626
 627                 if ( !( isset( $arrToInsert[0] ) && is_array( $arrToInsert[0] ) ) ) { // Not multi row
 628                         $arrToInsert = [ 0 => $arrToInsert ]; // make everything multi row compatible
 629                 }
 630
 631                 // We know the table we're inserting into, get its identity column
 632                 $identity = null;
 633                 // strip matching square brackets and the db/schema from table name
 634                 $tableRawArr = explode( '.', preg_replace( '#\[([^\]]*)\]#', '$1', $table ) );
 635                 $tableRaw = array_pop( $tableRawArr );
 636                 $res = $this->doQuery(
 637                         "SELECT NAME AS idColumn FROM SYS.IDENTITY_COLUMNS " .
 638                                 "WHERE OBJECT_NAME(OBJECT_ID)='{$tableRaw}'"
 639                 );
 640                 if ( $res && sqlsrv_has_rows( $res ) ) {
 641                         // There is an identity for this table.
 642                         $identityArr = sqlsrv_fetch_array( $res, SQLSRV_FETCH_ASSOC );
 643                         $identity = array_pop( $identityArr );
 644                 }
 645                 sqlsrv_free_stmt( $res );
 646
 647                 // Determine binary/varbinary fields so we can encode data as a hex string like 0xABCDEF
 648                 $binaryColumns = $this->getBinaryColumns( $table );
 649
 650                 // INSERT IGNORE is not supported by SQL Server
 651                 // remove IGNORE from options list and set ignore flag to true
 652                 if ( in_array( 'IGNORE', $options ) ) {
 653                         $options = array_diff( $options, [ 'IGNORE' ] );
 654                         $this->ignoreDupKeyErrors = true;
 655                 }
 656
 657                 $ret = null;
 658                 foreach ( $arrToInsert as $a ) {
 659                         // start out with empty identity column, this is so we can return
 660                         // it as a result of the INSERT logic
 661                         $sqlPre = '';
 662                         $sqlPost = '';
 663                         $identityClause = '';
 664
 665                         // if we have an identity column
 666                         if ( $identity ) {
 667                                 // iterate through
 668                                 foreach ( $a as $k => $v ) {
 669                                         if ( $k == $identity ) {
 670                                                 if ( !is_null( $v ) ) {
 671                                                         // there is a value being passed to us,
 672                                                         // we need to turn on and off inserted identity
 673                                                         $sqlPre = "SET IDENTITY_INSERT $table ON;";
 674                                                         $sqlPost = ";SET IDENTITY_INSERT $table OFF;";
 675                                                 } else {
 676                                                         // we can't insert NULL into an identity column,
 677                                                         // so remove the column from the insert.
 678                                                         unset( $a[$k] );
 679                                                 }
 680                                         }
 681                                 }
 682
 683                                 // we want to output an identity column as result
 684                                 $identityClause = "OUTPUT INSERTED.$identity ";
 685                         }
 686
 687                         $keys = array_keys( $a );
 688
 689                         // Build the actual query
 690                         $sql = $sqlPre . 'INSERT ' . implode( ' ', $options ) .
 691                                 " INTO $table (" . implode( ',', $keys ) . ") $identityClause VALUES (";
 692
 693                         $first = true;
 694                         foreach ( $a as $key => $value ) {
 695                                 if ( isset( $binaryColumns[$key] ) ) {
 696                                         $value = new MssqlBlob( $value );
 697                                 }
 698                                 if ( $first ) {
 699                                         $first = false;
 700                                 } else {
 701                                         $sql .= ',';
 702                                 }
 703                                 if ( is_null( $value ) ) {
 704                                         $sql .= 'null';
 705                                 } else {
 706                                         $sql .= $this->addQuotes( $value );
 707                                 }
 708                         }
 709                         $sql .= ')' . $sqlPost;
 710
 711                         // Run the query
 712                         $this->scrollableCursor = false;
 713                         try {
 714                                 $ret = $this->query( $sql );
 715                         } catch ( Exception $e ) {
 716                                 $this->scrollableCursor = true;
 717                                 $this->ignoreDupKeyErrors = false;
 718                                 throw $e;
 719                         }
 720                         $this->scrollableCursor = true;
 721
 722                         if ( $ret instanceof ResultWrapper && !is_null( $identity ) ) {
 723                                 // Then we want to get the identity column value we were assigned and save it off
 724                                 $row = $ret->fetchObject();
 725                                 if ( is_object( $row ) ) {
 726                                         $this->lastInsertId = $row->$identity;
 727                                         // It seems that mAffectedRows is -1 sometimes when OUTPUT INSERTED.identity is
 728                                         // used if we got an identity back, we know for sure a row was affected, so
 729                                         // adjust that here
 730                                         if ( $this->lastAffectedRowCount == -1 ) {
 731                                                 $this->lastAffectedRowCount = 1;
 732                                         }
 733                                 }
 734                         }
 735                 }
 736
 737                 $this->ignoreDupKeyErrors = false;
 738
 739                 return true;
 740         }
 741
 742         /**
 743          * INSERT SELECT wrapper
 744          * $varMap must be an associative array of the form [ 'dest1' => 'source1', ... ]
 745          * Source items may be literals rather than field names, but strings should
 746          * be quoted with Database::addQuotes().
 747          * @param string $destTable
 748          * @param array|string $srcTable May be an array of tables.
 749          * @param array $varMap
 750          * @param array $conds May be "*" to copy the whole table.
 751          * @param string $fname
 752          * @param array $insertOptions
 753          * @param array $selectOptions
 754          * @param array $selectJoinConds
 755          * @throws Exception
 756          */
 757         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds, $fname = __METHOD__,
 758                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
 759         ) {
 760                 $this->scrollableCursor = false;
 761                 try {
 762                         parent::nativeInsertSelect(
 763                                 $destTable,
 764                                 $srcTable,
 765                                 $varMap,
 766                                 $conds,
 767                                 $fname,
 768                                 $insertOptions,
 769                                 $selectOptions,
 770                                 $selectJoinConds
 771                         );
 772                 } catch ( Exception $e ) {
 773                         $this->scrollableCursor = true;
 774                         throw $e;
 775                 }
 776                 $this->scrollableCursor = true;
 777         }
 778
 779         /**
 780          * UPDATE wrapper. Takes a condition array and a SET array.
 781          *
 782          * @param string $table Name of the table to UPDATE. This will be passed through
 783          *                Database::tableName().
 784          *
 785          * @param array $values An array of values to SET. For each array element,
 786          *                the key gives the field name, and the value gives the data
 787          *                to set that field to. The data will be quoted by
 788          *                Database::addQuotes().
 789          *
 790          * @param array $conds An array of conditions (WHERE). See
 791          *                Database::select() for the details of the format of
 792          *                condition arrays. Use '*' to update all rows.
 793          *
 794          * @param string $fname The function name of the caller (from __METHOD__),
 795          *                for logging and profiling.
 796          *
 797          * @param array $options An array of UPDATE options, can be:
 798          *                   - IGNORE: Ignore unique key conflicts
 799          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
 800          * @return bool
 801          * @throws DBUnexpectedError
 802          * @throws Exception
 803          */
 804         function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
 805                 $table = $this->tableName( $table );
 806                 $binaryColumns = $this->getBinaryColumns( $table );
 807
 808                 $opts = $this->makeUpdateOptions( $options );
 809                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET, $binaryColumns );
 810
 811                 if ( $conds !== [] && $conds !== '*' ) {
 812                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND, $binaryColumns );
 813                 }
 814
 815                 $this->scrollableCursor = false;
 816                 try {
 817                         $this->query( $sql );
 818                 } catch ( Exception $e ) {
 819                         $this->scrollableCursor = true;
 820                         throw $e;
 821                 }
 822                 $this->scrollableCursor = true;
 823                 return true;
 824         }
 825
 826         /**
 827          * Makes an encoded list of strings from an array
 828          * @param array $a Containing the data
 829          * @param int $mode Constant
 830          *      - LIST_COMMA:          comma separated, no field names
 831          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
 832          *        the documentation for $conds in Database::select().
 833          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
 834          *      - LIST_SET:            comma separated with field names, like a SET clause
 835          *      - LIST_NAMES:          comma separated field names
 836          * @param array $binaryColumns Contains a list of column names that are binary types
 837          *      This is a custom parameter only present for MS SQL.
 838          *
 839          * @throws DBUnexpectedError
 840          * @return string
 841          */
 842         public function makeList( $a, $mode = LIST_COMMA, $binaryColumns = [] ) {
 843                 if ( !is_array( $a ) ) {
 844                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
 845                 }
 846
 847                 if ( $mode != LIST_NAMES ) {
 848                         // In MS SQL, values need to be specially encoded when they are
 849                         // inserted into binary fields. Perform this necessary encoding
 850                         // for the specified set of columns.
 851                         foreach ( array_keys( $a ) as $field ) {
 852                                 if ( !isset( $binaryColumns[$field] ) ) {
 853                                         continue;
 854                                 }
 855
 856                                 if ( is_array( $a[$field] ) ) {
 857                                         foreach ( $a[$field] as &$v ) {
 858                                                 $v = new MssqlBlob( $v );
 859                                         }
 860                                         unset( $v );
 861                                 } else {
 862                                         $a[$field] = new MssqlBlob( $a[$field] );
 863                                 }
 864                         }
 865                 }
 866
 867                 return parent::makeList( $a, $mode );
 868         }
 869
 870         /**
 871          * @param string $table
 872          * @param string $field
 873          * @return int Returns the size of a text field, or -1 for "unlimited"
 874          */
 875         public function textFieldSize( $table, $field ) {
 876                 $table = $this->tableName( $table );
 877                 $sql = "SELECT CHARACTER_MAXIMUM_LENGTH,DATA_TYPE FROM INFORMATION_SCHEMA.Columns
 878                         WHERE TABLE_NAME = '$table' AND COLUMN_NAME = '$field'";
 879                 $res = $this->query( $sql );
 880                 $row = $this->fetchRow( $res );
 881                 $size = -1;
 882                 if ( strtolower( $row['DATA_TYPE'] ) != 'text' ) {
 883                         $size = $row['CHARACTER_MAXIMUM_LENGTH'];
 884                 }
 885
 886                 return $size;
 887         }
 888
 889         /**
 890          * Construct a LIMIT query with optional offset
 891          * This is used for query pages
 892          *
 893          * @param string $sql SQL query we will append the limit too
 894          * @param int $limit The SQL limit
 895          * @param bool|int $offset The SQL offset (default false)
 896          * @return array|string
 897          * @throws DBUnexpectedError
 898          */
 899         public function limitResult( $sql, $limit, $offset = false ) {
 900                 if ( $offset === false || $offset == 0 ) {
 901                         if ( strpos( $sql, "SELECT" ) === false ) {
 902                                 return "TOP {$limit} " . $sql;
 903                         } else {
 904                                 return preg_replace( '/\bSELECT(\s+DISTINCT)?\b/Dsi',
 905                                         'SELECT$1 TOP ' . $limit, $sql, 1 );
 906                         }
 907                 } else {
 908                         // This one is fun, we need to pull out the select list as well as any ORDER BY clause
 909                         $select = $orderby = [];
 910                         $s1 = preg_match( '#SELECT\s+(.+?)\s+FROM#Dis', $sql, $select );
 911                         $s2 = preg_match( '#(ORDER BY\s+.+?)(\s*FOR XML .*)?$#Dis', $sql, $orderby );
 912                         $postOrder = '';
 913                         $first = $offset + 1;
 914                         $last = $offset + $limit;
 915                         $sub1 = 'sub_' . $this->subqueryId;
 916                         $sub2 = 'sub_' . ( $this->subqueryId + 1 );
 917                         $this->subqueryId += 2;
 918                         if ( !$s1 ) {
 919                                 // wat
 920                                 throw new DBUnexpectedError( $this, "Attempting to LIMIT a non-SELECT query\n" );
 921                         }
 922                         if ( !$s2 ) {
 923                                 // no ORDER BY
 924                                 $overOrder = 'ORDER BY (SELECT 1)';
 925                         } else {
 926                                 if ( !isset( $orderby[2] ) || !$orderby[2] ) {
 927                                         // don't need to strip it out if we're using a FOR XML clause
 928                                         $sql = str_replace( $orderby[1], '', $sql );
 929                                 }
 930                                 $overOrder = $orderby[1];
 931                                 $postOrder = ' ' . $overOrder;
 932                         }
 933                         $sql = "SELECT {$select[1]}
 934                                         FROM (
 935                                                 SELECT ROW_NUMBER() OVER({$overOrder}) AS rowNumber, *
 936                                                 FROM ({$sql}) {$sub1}
 937                                         ) {$sub2}
 938                                         WHERE rowNumber BETWEEN {$first} AND {$last}{$postOrder}";
 939
 940                         return $sql;
 941                 }
 942         }
 943
 944         /**
 945          * If there is a limit clause, parse it, strip it, and pass the remaining
 946          * SQL through limitResult() with the appropriate parameters. Not the
 947          * prettiest solution, but better than building a whole new parser. This
 948          * exists becase there are still too many extensions that don't use dynamic
 949          * sql generation.
 950          *
 951          * @param string $sql
 952          * @return array|mixed|string
 953          */
 954         public function LimitToTopN( $sql ) {
 955                 // Matches: LIMIT {[offset,] row_count | row_count OFFSET offset}
 956                 $pattern = '/\bLIMIT\s+((([0-9]+)\s*,\s*)?([0-9]+)(\s+OFFSET\s+([0-9]+))?)/i';
 957                 if ( preg_match( $pattern, $sql, $matches ) ) {
 958                         $row_count = $matches[4];
 959                         $offset = $matches[3] ?: $matches[6] ?: false;
 960
 961                         // strip the matching LIMIT clause out
 962                         $sql = str_replace( $matches[0], '', $sql );
 963
 964                         return $this->limitResult( $sql, $row_count, $offset );
 965                 }
 966
 967                 return $sql;
 968         }
 969
 970         /**
 971          * @return string Wikitext of a link to the server software's web site
 972          */
 973         public function getSoftwareLink() {
 974                 return "[{{int:version-db-mssql-url}} MS SQL Server]";
 975         }
 976
 977         /**
 978          * @return string Version information from the database
 979          */
 980         public function getServerVersion() {
 981                 $server_info = sqlsrv_server_info( $this->conn );
 982                 $version = $server_info['SQLServerVersion'] ?? 'Error';
 983
 984                 return $version;
 985         }
 986
 987         /**
 988          * @param string $table
 989          * @param string $fname
 990          * @return bool
 991          */
 992         public function tableExists( $table, $fname = __METHOD__ ) {
 993                 list( $db, $schema, $table ) = $this->tableName( $table, 'split' );
 994
 995                 if ( $db !== false ) {
 996                         // remote database
 997                         $this->queryLogger->error( "Attempting to call tableExists on a remote table" );
 998                         return false;
 999                 }
1000
1001                 if ( $schema === false ) {
1002                         $schema = $this->dbSchema();
1003                 }
1004
1005                 $res = $this->query( "SELECT 1 FROM INFORMATION_SCHEMA.TABLES
1006                         WHERE TABLE_TYPE = 'BASE TABLE'
1007                         AND TABLE_SCHEMA = '$schema' AND TABLE_NAME = '$table'" );
1008
1009                 if ( $res->numRows() ) {
1010                         return true;
1011                 } else {
1012                         return false;
1013                 }
1014         }
1015
1016         /**
1017          * Query whether a given column exists in the mediawiki schema
1018          * @param string $table
1019          * @param string $field
1020          * @param string $fname
1021          * @return bool
1022          */
1023         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1024                 list( $db, $schema, $table ) = $this->tableName( $table, 'split' );
1025
1026                 if ( $db !== false ) {
1027                         // remote database
1028                         $this->queryLogger->error( "Attempting to call fieldExists on a remote table" );
1029                         return false;
1030                 }
1031
1032                 $res = $this->query( "SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS
1033                         WHERE TABLE_SCHEMA = '$schema' AND TABLE_NAME = '$table' AND COLUMN_NAME = '$field'" );
1034
1035                 if ( $res->numRows() ) {
1036                         return true;
1037                 } else {
1038                         return false;
1039                 }
1040         }
1041
1042         public function fieldInfo( $table, $field ) {
1043                 list( $db, $schema, $table ) = $this->tableName( $table, 'split' );
1044
1045                 if ( $db !== false ) {
1046                         // remote database
1047                         $this->queryLogger->error( "Attempting to call fieldInfo on a remote table" );
1048                         return false;
1049                 }
1050
1051                 $res = $this->query( "SELECT * FROM INFORMATION_SCHEMA.COLUMNS
1052                         WHERE TABLE_SCHEMA = '$schema' AND TABLE_NAME = '$table' AND COLUMN_NAME = '$field'" );
1053
1054                 $meta = $res->fetchRow();
1055                 if ( $meta ) {
1056                         return new MssqlField( $meta );
1057                 }
1058
1059                 return false;
1060         }
1061
1062         protected function doSavepoint( $identifier, $fname ) {
1063                 $this->query( 'SAVE TRANSACTION ' . $this->addIdentifierQuotes( $identifier ), $fname );
1064         }
1065
1066         protected function doReleaseSavepoint( $identifier, $fname ) {
1067                 // Not supported. Also not really needed, a new doSavepoint() for the
1068                 // same identifier will overwrite the old.
1069         }
1070
1071         protected function doRollbackToSavepoint( $identifier, $fname ) {
1072                 $this->query( 'ROLLBACK TRANSACTION ' . $this->addIdentifierQuotes( $identifier ), $fname );
1073         }
1074
1075         /**
1076          * Begin a transaction, committing any previously open transaction
1077          * @param string $fname
1078          */
1079         protected function doBegin( $fname = __METHOD__ ) {
1080                 sqlsrv_begin_transaction( $this->conn );
1081                 $this->trxLevel = 1;
1082         }
1083
1084         /**
1085          * End a transaction
1086          * @param string $fname
1087          */
1088         protected function doCommit( $fname = __METHOD__ ) {
1089                 sqlsrv_commit( $this->conn );
1090                 $this->trxLevel = 0;
1091         }
1092
1093         /**
1094          * Rollback a transaction.
1095          * No-op on non-transactional databases.
1096          * @param string $fname
1097          */
1098         protected function doRollback( $fname = __METHOD__ ) {
1099                 sqlsrv_rollback( $this->conn );
1100                 $this->trxLevel = 0;
1101         }
1102
1103         /**
1104          * @param string $s
1105          * @return string
1106          */
1107         public function strencode( $s ) {
1108                 // Should not be called by us
1109                 return str_replace( "'", "''", $s );
1110         }
1111
1112         /**
1113          * @param string|int|null|bool|Blob $s
1114          * @return string|int
1115          */
1116         public function addQuotes( $s ) {
1117                 if ( $s instanceof MssqlBlob ) {
1118                         return $s->fetch();
1119                 } elseif ( $s instanceof Blob ) {
1120                         // this shouldn't really ever be called, but it's here if needed
1121                         // (and will quite possibly make the SQL error out)
1122                         $blob = new MssqlBlob( $s->fetch() );
1123                         return $blob->fetch();
1124                 } else {
1125                         if ( is_bool( $s ) ) {
1126                                 $s = $s ? 1 : 0;
1127                         }
1128                         return parent::addQuotes( $s );
1129                 }
1130         }
1131
1132         /**
1133          * @param string $s
1134          * @return string
1135          */
1136         public function addIdentifierQuotes( $s ) {
1137                 // http://msdn.microsoft.com/en-us/library/aa223962.aspx
1138                 return '[' . $s . ']';
1139         }
1140
1141         /**
1142          * @param string $name
1143          * @return bool
1144          */
1145         public function isQuotedIdentifier( $name ) {
1146                 return strlen( $name ) && $name[0] == '[' && substr( $name, -1, 1 ) == ']';
1147         }
1148
1149         /**
1150          * MS SQL supports more pattern operators than other databases (ex: [,],^)
1151          *
1152          * @param string $s
1153          * @param string $escapeChar
1154          * @return string
1155          */
1156         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
1157                 return str_replace( [ $escapeChar, '%', '_', '[', ']', '^' ],
1158                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_",
1159                                 "{$escapeChar}[", "{$escapeChar}]", "{$escapeChar}^" ],
1160                         $s );
1161         }
1162
1163         protected function doSelectDomain( DatabaseDomain $domain ) {
1164                 if ( $domain->getSchema() !== null ) {
1165                         throw new DBExpectedError( $this, __CLASS__ . ": domain schemas are not supported." );
1166                 }
1167
1168                 $database = $domain->getDatabase();
1169                 if ( $database !== $this->getDBname() ) {
1170                         $encDatabase = $this->addIdentifierQuotes( $database );
1171                         $res = $this->doQuery( "USE $encDatabase" );
1172                         if ( !$res ) {
1173                                 throw new DBExpectedError( $this, "Could not select database '$database'." );
1174                         }
1175                 }
1176                 // Update that domain fields on success (no exception thrown)
1177                 $this->currentDomain = $domain;
1178
1179                 return true;
1180         }
1181
1182         /**
1183          * @param array $options An associative array of options to be turned into
1184          *   an SQL query, valid keys are listed in the function.
1185          * @return array
1186          */
1187         public function makeSelectOptions( $options ) {
1188                 $tailOpts = '';
1189                 $startOpts = '';
1190
1191                 $noKeyOptions = [];
1192                 foreach ( $options as $key => $option ) {
1193                         if ( is_numeric( $key ) ) {
1194                                 $noKeyOptions[$option] = true;
1195                         }
1196                 }
1197
1198                 $tailOpts .= $this->makeGroupByWithHaving( $options );
1199
1200                 $tailOpts .= $this->makeOrderBy( $options );
1201
1202                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1203                         $startOpts .= 'DISTINCT';
1204                 }
1205
1206                 if ( isset( $noKeyOptions['FOR XML'] ) ) {
1207                         // used in group concat field emulation
1208                         $tailOpts .= " FOR XML PATH('')";
1209                 }
1210
1211                 // we want this to be compatible with the output of parent::makeSelectOptions()
1212                 return [ $startOpts, '', $tailOpts, '', '' ];
1213         }
1214
1215         public function getType() {
1216                 return 'mssql';
1217         }
1218
1219         /**
1220          * @param array $stringList
1221          * @return string
1222          */
1223         public function buildConcat( $stringList ) {
1224                 return implode( ' + ', $stringList );
1225         }
1226
1227         /**
1228          * Build a GROUP_CONCAT or equivalent statement for a query.
1229          * MS SQL doesn't have GROUP_CONCAT so we emulate it with other stuff (and boy is it nasty)
1230          *
1231          * This is useful for combining a field for several rows into a single string.
1232          * NULL values will not appear in the output, duplicated values will appear,
1233          * and the resulting delimiter-separated values have no defined sort order.
1234          * Code using the results may need to use the PHP unique() or sort() methods.
1235          *
1236          * @param string $delim Glue to bind the results together
1237          * @param string|array $table Table name
1238          * @param string $field Field name
1239          * @param string|array $conds Conditions
1240          * @param string|array $join_conds Join conditions
1241          * @return string SQL text
1242          * @since 1.23
1243          */
1244         public function buildGroupConcatField( $delim, $table, $field, $conds = '',
1245                 $join_conds = []
1246         ) {
1247                 $gcsq = 'gcsq_' . $this->subqueryId;
1248                 $this->subqueryId++;
1249
1250                 $delimLen = strlen( $delim );
1251                 $fld = "{$field} + {$this->addQuotes( $delim )}";
1252                 $sql = "(SELECT LEFT({$field}, LEN({$field}) - {$delimLen}) FROM ("
1253                         . $this->selectSQLText( $table, $fld, $conds, null, [ 'FOR XML' ], $join_conds )
1254                         . ") {$gcsq} ({$field}))";
1255
1256                 return $sql;
1257         }
1258
1259         public function buildSubstring( $input, $startPosition, $length = null ) {
1260                 $this->assertBuildSubstringParams( $startPosition, $length );
1261                 if ( $length === null ) {
1262                         /**
1263                          * MSSQL doesn't allow an empty length parameter, so when we don't want to limit the
1264                          * length returned use the default maximum size of text.
1265                          * @see https://docs.microsoft.com/en-us/sql/t-sql/statements/set-textsize-transact-sql
1266                          */
1267                         $length = 2147483647;
1268                 }
1269                 return 'SUBSTRING(' . implode( ',', [ $input, $startPosition, $length ] ) . ')';
1270         }
1271
1272         /**
1273          * Returns an associative array for fields that are of type varbinary, binary, or image
1274          * $table can be either a raw table name or passed through tableName() first
1275          * @param string $table
1276          * @return array
1277          */
1278         private function getBinaryColumns( $table ) {
1279                 $tableRawArr = explode( '.', preg_replace( '#\[([^\]]*)\]#', '$1', $table ) );
1280                 $tableRaw = array_pop( $tableRawArr );
1281
1282                 if ( $this->binaryColumnCache === null ) {
1283                         $this->populateColumnCaches();
1284                 }
1285
1286                 return $this->binaryColumnCache[$tableRaw] ?? [];
1287         }
1288
1289         /**
1290          * @param string $table
1291          * @return array
1292          */
1293         private function getBitColumns( $table ) {
1294                 $tableRawArr = explode( '.', preg_replace( '#\[([^\]]*)\]#', '$1', $table ) );
1295                 $tableRaw = array_pop( $tableRawArr );
1296
1297                 if ( $this->bitColumnCache === null ) {
1298                         $this->populateColumnCaches();
1299                 }
1300
1301                 return $this->bitColumnCache[$tableRaw] ?? [];
1302         }
1303
1304         private function populateColumnCaches() {
1305                 $res = $this->select( 'INFORMATION_SCHEMA.COLUMNS', '*',
1306                         [
1307                                 'TABLE_CATALOG' => $this->getDBname(),
1308                                 'TABLE_SCHEMA' => $this->dbSchema(),
1309                                 'DATA_TYPE' => [ 'varbinary', 'binary', 'image', 'bit' ]
1310                         ] );
1311
1312                 $this->binaryColumnCache = [];
1313                 $this->bitColumnCache = [];
1314                 foreach ( $res as $row ) {
1315                         if ( $row->DATA_TYPE == 'bit' ) {
1316                                 $this->bitColumnCache[$row->TABLE_NAME][$row->COLUMN_NAME] = $row;
1317                         } else {
1318                                 $this->binaryColumnCache[$row->TABLE_NAME][$row->COLUMN_NAME] = $row;
1319                         }
1320                 }
1321         }
1322
1323         /**
1324          * @param string $name
1325          * @param string $format One of "quoted" (default), "raw", or "split".
1326          * @return string|array When the requested $format is "split", a list of database, schema, and
1327          *  table name is returned. Database and schema can be `false`.
1328          */
1329         function tableName( $name, $format = 'quoted' ) {
1330                 # Replace reserved words with better ones
1331                 switch ( $name ) {
1332                         case 'user':
1333                                 return $this->realTableName( 'mwuser', $format );
1334                         default:
1335                                 return $this->realTableName( $name, $format );
1336                 }
1337         }
1338
1339         /**
1340          * call this instead of tableName() in the updater when renaming tables
1341          * @param string $name
1342          * @param string $format One of "quoted" (default), "raw", or "split".
1343          * @return string|array When the requested $format is "split", a list of database, schema, and
1344          *  table name is returned. Database and schema can be `false`.
1345          * @private
1346          */
1347         function realTableName( $name, $format = 'quoted' ) {
1348                 $table = parent::tableName( $name, $format );
1349                 if ( $format == 'split' ) {
1350                         // Used internally, we want the schema split off from the table name and returned
1351                         // as a list with 3 elements (database, schema, table)
1352                         return array_pad( explode( '.', $table, 3 ), -3, false );
1353                 }
1354                 return $table;
1355         }
1356
1357         /**
1358          * Delete a table
1359          * @param string $tableName
1360          * @param string $fName
1361          * @return bool|ResultWrapper
1362          * @since 1.18
1363          */
1364         public function dropTable( $tableName, $fName = __METHOD__ ) {
1365                 if ( !$this->tableExists( $tableName, $fName ) ) {
1366                         return false;
1367                 }
1368
1369                 // parent function incorrectly appends CASCADE, which we don't want
1370                 $sql = "DROP TABLE " . $this->tableName( $tableName );
1371
1372                 return $this->query( $sql, $fName );
1373         }
1374
1375         /**
1376          * Called in the installer and updater.
1377          * Probably doesn't need to be called anywhere else in the codebase.
1378          * @param bool|null $value
1379          * @return bool|null
1380          */
1381         public function prepareStatements( $value = null ) {
1382                 $old = $this->prepareStatements;
1383                 if ( $value !== null ) {
1384                         $this->prepareStatements = $value;
1385                 }
1386
1387                 return $old;
1388         }
1389
1390         /**
1391          * Called in the installer and updater.
1392          * Probably doesn't need to be called anywhere else in the codebase.
1393          * @param bool|null $value
1394          * @return bool|null
1395          */
1396         public function scrollableCursor( $value = null ) {
1397                 $old = $this->scrollableCursor;
1398                 if ( $value !== null ) {
1399                         $this->scrollableCursor = $value;
1400                 }
1401
1402                 return $old;
1403         }
1404
1405         public function buildStringCast( $field ) {
1406                 return "CAST( $field AS NVARCHAR )";
1407         }
1408
1409         public static function getAttributes() {
1410                 return [ self::ATTR_SCHEMAS_AS_TABLE_GROUPS => true ];
1411         }
1412 }
1413
1414 /**
1415  * @deprecated since 1.29
1416  */
1417 class_alias( DatabaseMssql::class, 'DatabaseMssql' );